1. Field of the Invention
The present invention relates to an apparatus for matching Gigabit Ethernet (GbE) frames with an Optical Transport Hierarchy (OTH) which is a standard digital transport hierarchy defined in ITU-T recommendation G.709.
This work was supported by the IT R&D program of MIC/IITA. [2006-S-060-02, OTH-based 40G Multi-service Transmission Technology]
2. Description of the Related Art
A technology of mapping 1 gigabit Ethernet signals with encapsulated payloads by defining an Optical Channel Data Unit0 (ODU0) having about 1.22 Gbit/s capacity has been suggested in order to match 1 gigabit Ethernet signals with an Optical Transport Hierarchy (OTH) defined in ITU-T recommendation G.709. According to this technology, a single GFP-T is mapped into an ODU0, two ODU0s are mapped into a single ODU1, eight ODU0s are mapped into a single ODU2, or thirty two ODU0s are mapped into a single ODU3.
An Ethernet bridge interconnects two or more local area networks (LANs). A port of the bridge may be interconnected to another bridge or directly interconnected to a terminal or a router. Since the bridge processes a data link layer(Layer 2), the bridge regards a router which processes a network layer (Layer 3) as a terminal. In addition, a port of the bridge may be interconnected with a peer to peer link or a universal bus LAN. When an Ethernet frame is transported, a medium access control (MAC) destination address (DA) is placed in a front portion of the frame and a MAC source address (SA) is placed next to the DA.
A fundamental function of the bridge is to hand over a received frame to a port to which a destination address is assigned. Whenever a frame is input to a port, the bridge learns a MAC SA of the frame by recording that the SA is assigned to the port in a filtering data base (FDB) table. In addition, the bridge looks up an FDB table entry corresponding to a DA of the frame and sends the frame to a port to which the DA is assigned. The DA information is learned when a frame having the address as an SA is input. If a frame having a DA which is not learned is input, the frame is sent to all other ports except the port to which the frame having the DA is input to perform communication. If a DA is assigned to the port through which a frame is input, the frame is discarded since it is regarded that the frame is already transported to the destination. Thus, terminals or routers interconnected with each other via bridges can communicate with each other using MAC addresses even though they do not know each other's physical locations. If a DA type is broadcasting in a LAN, frames are broadcast to all segments. If a bridge does not know a DA, it floods frames.
However, since limited GbE signals match with each of the ODU1, ODU2, and ODU3 when GbE signals match with the OTH system according to the conventional technology, signal transportation may be limited and bandwidth loss may occur.